Alkylation of phenothiazine

ABSTRACT

ALKYL-SUBSTITUTED PHENOTHIAZINES USEFUL AS ANTIOXIDANTS FOR INCORPORATION INTO MINERAL AND SYNTHETIC OILS AE OBTAINED IN A PROCESS WHICH COMPRISES REACTING PHENOTHIAZINE AND AN ALKYL HALIDE IN THE PRESENCE OF AN ALUMINUM HALIDE CATALYST.

United States Patent 3,689,484 ALKYLATION 0F PHENOTHIAZINE Ilgvars J. Spilners, Monroeville, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa. No Drawing. Filed Dec. 28, 1970, Ser. No. 102,230 Int. Cl. (107d 93/14 US. Cl. 260-243 A 7 Claims ABSTRACT OF THE DISCLOSURE Alkyl-substituted phenothiazines useful as antioxidants for incorporation into mineral and synthetic oils are obtained in a process which comprises reacting phenothiazine and an alkyl halide in the presence of an aluminum halide catalyst.

This invention relates to a process for the production of alkyl-substituted phenothiazines, especially nuclear alkylated phenothiazines having the formula where R is an alkyl radical having from 1 to 12 carbon atoms, a is an integer of 0 to 4 and b is an integer of 1 to 4. A specific example of an alkyl-substituted compound of the above formula where R is a tertiary octyl radical and a and b are 1 is 3,7-di-t-octylpheothiazine.

The tread in designing more eflicient and more economical engines has accentuated the need for lubricants which will effectively lubricate such engines under severe operating conditions over extended periods of time. While uncompounded mineral oils which have been subjected to various refining procedures including solvent extraction, hydrogenation, treating with aluminium chloride and the like have been satisfactory lubricants in some applications, the treated mineral oils per se are not completely satisfactory under the wide temperature ranges and extreme operating conditions frequently encountered in jet aircraft engines. While synthetic lubricants have recently gained prominence in the field of aircraft engine lubrication because of their resistance to oxidation at temperatures up to about 300 F., these lubricants, if uncompounded, also deteriorate under oxidizing conditions at temperatures of 425 to 450 F.

The use of phenothiazine in mineral and synthetic lubricating oils has met with some success in reducing the normal oxidation tendencies of the oils. However, the presence of phenolthiazine in some oils, particularly synthetic ester lubricants, has been found to promote the deposition of sludge in internal combustion engines operating under oxidizing conditions at temperatures above about 300 F. for prolonged periods of time. The sludge thus formed is referred to as phenothiazine sludge or phenothiazine dirtiness. Attempts have been made to overcome phenothiazine sludge formed at elevated temperatures by incorporating various detergents in the lubricating oil in combination with the phenothiazine. However, such combinations have not been completely satisfactory in that not all detergents are compatible with phenothiazine.

The problem of phenothiazine dirtiness has been considerably reduced by the use of phenothiazines containing one or more alkyl substituents attached to one or both of the benzene rings, the substituents containing from 1 to 12, preferably a total of at least 4 carbon atoms in the alkyl groups. Typical alkyl-substituted phenothiazines within the preferred group are monoand di-t-b utylphenothiazine ad monoand di-t-octylphenothiazine.

Several methods for preparing alkyl-substituted phenothiazines have been disclosed previously. Niederl discloses in US. Pat. No. 2,484,838 that 4-t-octylphenothiazine can be prepared according to a ring closure technique by heating o-aminothiophenol and 4-t-octyl-1,2-benzenediol in an autoclave at 220 to 240 C. for about 30 hours. Farbenfabriken Bayer Aktiengesellschaft discloses in British Pat. No. 807,668 that 4-ethylphenothiazine can be prepared by heating phenothiazine and ethylene at a high temperature and pressure (300 C. and 200 atmospheres) for 2 to 3 hours in the presence of an aluminum-anilide catalyst. Scotchford et al. disclose in US. Pat. No. 3,393,- 193 that phenothiazine can be dialkylated by heating phenothiazine and an alkene having a methyl group adjacent to the double bond. The reaction is conducted at a temperature of 50 to C. and atmospheric pressure in the presence of a boron trifluoride-complex catalyst, e.g., boron-trifluoride-dihydrate. Randell discloses in US. Pats. Nos. 3,489,749 and 3,523,910 that alkyl-substituted phenothiazines having a t-butyl group in the l-position and the same or diiferent alkyl groups in the 3- and 7-position can be prepared by reacting phenothiazine, 3-alkylphenothiazines or 3,7-dialkyl-phenothiazines with isobutylene at a temperature of 50 to 200 C. and atmospheric pressure in the presence of a Bronsted acid catalyst. While the prior methods of preparing alkyl-substituted phenothiazines have been moderately satisfactory they have required complex catalysts and/ or high temperatures and pressures over prolonged reaction periods.

In accordance with the present invention, an improved process is provided for producing alkyl-substituted phenothiazines by direct alkylation utilizing an alkyl halide as the alkylating agent. The process comprises reacting phenothiazine and a large excess over the stoichiometric amount of an alkyl halide in the presence of a slight excess of an aluminum halide catalyst. While there may be intermediate steps in the reaction which takes place, the reaction is believed to proceed in accordance with the following illustrative equation:

where R is an alkyl radical having from 1 to 12 carbon atoms, a is an integer of 0 to 4, b is an integer of 1 to 4 and X is a halogen selected from the group consisting of chlorine, bromine and iodine.

The number and position of the alkyl radicals introduced into the phenothiazine molecule by the process of the invention depends to some extent upon the amount of the alkyl halide used and upon the reaction conditions employed. The alkyl halide is preferably used in amounts of about 2 to about 10 moles of alkyl halide per mole of phenothiazine. In most instances when introducing one alkyl radical into the phenothiazine molecule, the alkyl radical occupies the 2- or 3-position. When two alkyl radicals are introduced into the phenothiazine molecule the positions occupied are the 2,7-, 2.8-, 3,7- or 3,8-positions. The positions occupied when three or four alkyl radicals are introduced are, in most instances, the 1,3,7- and the 1,3,7,'9 -positions, respectively.

When an R group is attached to each benzene ring as illustrated in the structural formula shown hereinabove, the groups are the same or mixed. The R groups may be straight chain or branched chain in structurelExamples of the R groups'containing from 1 to 12 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl, amyl, isoamyl, hexyl, isohexyl, heptyl, isoheptyl, octyl, isooctyl, tertiary octyl, nonyl, isononyl, decyl, dodecyl and the like. Preferably, however, the R groups are tertiary alkyl radicals having from 4 to 8 carbon atoms.

Specific examples of alkyl-substituted phenothiazines which can be prepared in accordance with the process of the invention are:

Z-methyl-phenothiazine 2-ethyl-phenothiazine 2-isopropyl-phenothiazine Z-sec-butyl-phenothiazine 2-t-butyl-phenothiazine Z-n-butyl-phenothiazine 2-n-pentyl-phenothiazine 2-n-hexyl-phenothiazine 2-n-heptyl-phenothiazine 2-t-octyl-phenothiazine 2-n-nonyl-phenothiazine 2-n-dodecyl-phenothiazine 3-methyl-phenothiazine S-ethyl-phenothiazine 3-isopropyl-phenothiazine 3-sec-butyl-phenothiazine 3-t-butyl-phenothiazine 3-n-butyl-phenothiazine 3-n-pentyl-phenothiazine S-n-hexyl-phenothiazine 3-n-heptyl-phenothiazine 3-t-octyl-phenothiazine 3-n-nonyl-phenothiazine 3-n-dodecyl-phenothiazine 2,3-di-methyl-phenothiazine 2,3-di-ethyl-phenothiazine 2,3-di-isopropyl-phenothiazine 2,3-di-t-butyl-phenothiazine 2,3-di-t-octyl-phenothiazine 2,7di-t-butyl-phenothiazine 2,8-di-t-butyl-phenothiazine 3,7-di-methyhphenothiazine 3,7-di-ethyl-phenothiazine 3,7-di-isopropyl-phenothiazine 3,7-di-t-butyl-phenothiazine 3,7-di-t-octyl-phenothiazine 3,8-di-t-butyl-phenothiazine 1,3,7-tri-methyl-phenothiazine 1,3,7-tri-ethyl-phenothiazine 1,3,7-tri-isopropyl-phenothiazine l,3,7-tri-t-butyl-phenothiazine 1,3,7-tri-t-octyl-phenothiazine 1,3,7,9-tetra-methyl-phenothiazine 1,3,7 ,9-tetra-ethyl-phenothiazine 1,3,7,9-tetra-isopropyl-phenothiazine I 1,3,7 ,9-tetra-t-butyl-phenothiazine 1,3,7,9-tetra-t-octyl-phenothiazine Phenothiazineand the alkyl halides used in the process of the invention are available commercially and can be variously prepared so that neither of these starting materials per se nor the processes by which they are obtained constitute a portion of the present invention. It is preferred, however, to use substantially pure compounds. While I can use any alkyl halide selected from the group consisting, of alkyl chlorides, bromides and iodides, I prefer the alkyl chlorides for economic reasons. Thus, preferred alkyl halides are methyl chloride, ethyl chloride, n-propyl chloride, isopropyl chloride, nbutyl chloride, tertiary butyl chloride, n-arnyl chloride, isoamyl chloride, n-hexyl chloride, isohexyl chloride, n-heptyl chloride, isoheptyl chloride, n-octyl chloride, isooctyl chloride, tertiary octyl chloride, n-nonyl chloride, isononyl chloride, n-decyl chloride and n-dodecyl chloride.

The aluminum halides which are used as catalysts in the process of the invention are available commercially so that neither the aluminum halide catalyst per se nor its method of preparation constitutes a portion of the present invention. While I can use either aluminum chloride, aluminum bromide or aluminum iodide I prefer to use aluminum chloride for reasons of economy. The aluminum chloride is used in its anhydrous form.

The proportion of aluminum halide catalyst which is employed in the process of the present invention is conveniently within the range of about 0.01 to about 1.5 moles of catalyst per mole of phenothiazine, a proportion of 1.1 mole of catalyst per mole of phenothiazine being particularly preferred.

The process of the present invention is advantageously carried out in the absence of a solvent although a solvent which is substantially inert under the conditions of the reaction may be employed after the alkylation reaction has been initiated. Examples of inert solvents which may be used include methylene chloride, carbon disulfide, chloroform, carbon tetrachloride and tetrachloroethane. The process is preferably carried out in an inert atmosphere, e.g., in nitrogen.

The process of the invention is preferably carried out at substantially atmospheric pressure but can be, if desired, effected at an elevated pressure. The process is preferably efiected at a temperature within the range of about 50 to about 200 C., a temperature within the range of 55 to C. being particularly preferred. The process may be conducted over a period of about one-half to about twenty hours or more, the exact amount of time depending upon completion of the transfer of the desired number of alkyl radicals to the phenothiazine. Final completion of the reaction is evidenced by the absence of evolved hydrogen halide.

In a batch process, all of the reactants can be added to the reaction vessel at the beginning or the reactants can be added gradually over a period of /2 to 6 hours or more depending upon the size of the batch prepared. I prefer, in a batch process, to add all of the phenothiazine, about onethird of the aluminm halide and at least one-half of the alkyl halide at the start of the reaction. Thereafter, as the reaction proceeds, I gradually add the remainder of the alkyl halide and aluminum halide. By carrying out the reaction in this manner, the reaction conditions are easier to control and less side reactions take place.

In a continuous process, the reactants and catalyst are continuously fed into a reaction vessel in proportions to provide from about 2 to about 10 moles of alkyl halide and from about 0.01 to about 1.5 moles of aluminum halide per mole of phenothiazine.

The alkyl substituted phenothiazine products of the process of the invention can be recovered from the reaction mixture by any conventional method, for example, by fractional crystallization from a suitable solvent such as petro- Ieum ether, methylene chloride, benzene, hexane, methanol, ethanol and the like, or purification by sublimation.

The lubricating oil to which the alkyl substituted phenothiazines produced in accordance with the present invention are added may be a mineral oil or a synthetic oil. By the term synthetic oil I mean a composition having a a majority of the properties of a hydrocarbon oil of lubrieating grade including polyalkylene oxides, silcones, esters of phosphoric and silicic acids, highly fiuorinated hydrocarbons, polyaryl ethers, aliphatic esters, etc. Especially preferred esters to which the alkyl substituted phenothiazines are added are the esters of monocarboxylic acids having three to twelve carbon atoms and polyalcohols such as pentaerythritol,.dipentaerythritol and trimethylolpropane. Examples of these esters are pentaerythrityl tetrabutyrate, pentaerythrityl tetraeaproate, pentaerythrityl dibutyratedicaproate, pentaerythrityl butyratecaproate divalerate, pentaerythrityl butyrate trivalerate, pentaerythrityl tributyratecaproate, mixed C saturated fatty acid esters of pentaerythritol, dipentaerythrityl hexavalerate, dipe'nt-aerythrityl hexahepto ate, dipentaerythrityl tributyratecaproate, dipentaerythrityl trivalerate trinonylate, dipentaerythrityl mixed hexaesters of C fatty acids and trimethylolpropane heptylate. Pentaerythritol esters of mixtures of C acids are excellent base oils. The latter esters are commercially available from Hercules Chemical Company.

The amount of the alkyl substituted phenothiazine employed as an antioxidant depends upon the particular lubricating oil base used as well as the severity of the conditions to which it is subjected and also upon the particular alkyl substituted phenothiazine chosen. Normally, the amount of alkyl phenothiazine comprises about 0.1 to about percent by weight based on the weight of the total composition. In most instances, good results are obtained with about 0.5 to about 2 percent by weight.

The lubricating oil can contain minor amounts of other addition agents normally added to a lubricating oil for a specific purpose, if desired, such as a pour point depressant, a viscosity index improver, an oiliness and extreme pressure agent, a corrosion inhibitor, a sludge inhibitor, a dispersant, a detergent, a thickener and the like. Also, if desired, the lubricating composition can contain a foam inhibitor such as an organo-silicon oxide condensation product, an organo-silicol condensation product and the like.

While the alkyl phenothiazines are efi'ective antioxidants for synthetic ester lubricants when used alone, their efficiency may be considerably improved when they are used in combination with one or more secondary aromatic amines containing two aromatic groups directly attached to nitrogen. When an alkyl phenothiazine is used in combination with the aromatic amine, the two additives act synergistically to provide greater resistance to oxidation at elevated temperatures than would be obtained by either additive used alone in comparable proportions. Typical aromatic amines which can be used in conjunction with the alkyl phenothiazines are N-phenyl-I-naphthylamine, N-phenyl-Z-naphthylamine, p,p'-dioctyldiphenylamine, pisopropoxydiphenylamine, p-n-butoxydiphenylamine, p-noctoxydiphenylamine, p-n-decoxydiphenylamine, p-n-dodecoxydiphenylamine and p-n-hexadecoxydiphenylamine. When a secondary aromatic amine is used in conjunction with an alkyl phenothiazine, the secondary aromatic amine comprises about 0.1 to about 5 percent by weight of the total composition. In most instances, good results are obtained with about 0.5 to about 2 percent by weight.

The invention may be more fully understood by reference to the following illustrative examples.

EXAMPLE 1 Reagents used:

Phenothiazine (50 grams; 0.25 mole) t-Butyl chloride (115 grams; 1.24 moles) Anhydrous aluminum chloride (35 grams; 0.26 mole) Into a 500-milliliter flask equipped with a stirrer, addition funnel and a nitrogen inlet tube are placed 50 grams (0.25 mole) of phenothiazine, 70 grams (0.76 mole) of tbtuyl chloride and grams (0.075 mole) of anhydrous aluminum chloride. The slurry thus formed is stirred and heated at 55 C. under an atmosphere of nitrogen for fifteen minutes. During the next three hours, 25 grams (0.19 mole) of anhydrous aluminum chloride in 2.5-gram portions and 45 grams (0.49 mole) of t-butyl chloride (dropwise) are added to the reaction mixture while heating from 55 to 130 C. Unreacted t-butyl chloride boils ofi of the reaction mixture and is collected in a cold trap. Thereafter, 250 ml. of methylene chloride is added to the reaction mixture and the mixture is then stirred and refluxed for sixteen hours. The reaction is then terminated by pouring the methylene chloride solution into ice Water. The methylene chloride solution is washed three times with water and then filtered. The methylene chloride is evaporated from the filtrate leaving a residual product which is then dissolved in benzene. The benzene solution is filtered,

(1) one major peak (retention time, 21.6 minutes) (2) two minor peaks (retention times, 19.8 and 21.8

minutes) (3) two trace peaks (retention times, 18.5 and 22.2

minutes) Mass spectra of the product show the following peaks:

Intensity Low voltage Assigned structure Phenothiazine. t-Butylphenothiazine. Di-t-butylphenothiezine. Tri-t-butylphenothiazine. Tetra-t-butylphenothiazine.

1 High voltage mass spectrum shows many other peaks. Most of the other pea ks appear to be due to fragment ions where the methyl groups have split ofi. The phenothiazine peak at high voltage may also be a fragment peak.

The above mass spectra data indicate that substantially no phenothiazine is found in the product. While the product comprises a mixture of mono-, di-, triand tetrat-butylphenothiazine, the product is predominantly di-t-butylphenothiazine with lesser amounts of mono-, triand tetra-t-butylphenothiazine. Upon further examination of the product, the infrared spectrum in Nujol and Fluorolube has peaks at 3500 cm.- (NH), about 3000 cm.- (alkyl and aromatic CH), 1600 cm.- (aromatic CH), 1450-1500 cm? and 1350-1400 cm? (alkyl CH), 1300 cm? (m.), 1260 cm.- (w.), 1160 cm. (w.), 1120 CIl'lI (W.), 885 CHI-T1 (w.), 845 cm." (W.), 810-830 cm.- (s.), 745 cm.- (m.) and 725 cm.- (m.).

[No'rEz s.-=strong peak, m.=medium peak, w.=weak peak].

The product has the following ultimate analysis:

Percent Carbon 77:99 Hydrogen 8.09 Sulfur 8.89 Nitrogen 4.16

An analytical sample of di-t-butylphenothiazine is obtained by collecting the effiuent corresponding to the major gas chromatograph peak (retention time, 21. 6 minutes). Identification of this sample using a Perkin-Elmer Model 137 Spectrophotometer in Nujol and Fluorolube shows peaks at 3500 cm. (NH), around 3000 cm. (aromatic and strong aliphatic CH), 1600 cm. (aromatic), 1450-1500 cm.- and 1350-1400 cm.- (strong aliphatic CH), 1300-1350 cm." 1210 cmr (w.), 1160 cm. (w.), 1120 cm.- (w.), 885 cm.* '(m.), 845 cmf (w.), 810-830 cm." (strong absorption due to unsymmetrical aromatic trisubstitution) and 720 cm." (m.). The 810-830 cm.- band indicates that t-butyl groups are substituted in the 2-,3- and 7-,8-positions. The isolated di-t-butylphenothiazine is a white solid, M.P. -182" C.

EXAMPLE H Reagents used:

Phenothiazine (20.0 grams; 0.01 mole) n-Butyl chloride (86.3 grams; 0.93 mole) Anhydrous aluminum chloride (15.0 grams; 0.112 mole) Into a SOD-milliliter flask equipped with a stirrer, addition funnel and a nitrogen inlet tube are placed 20 grams (0.1 mole) of phenothiazine, 86.3 grams (0.93 mole) of n-butyl chloride and 5 grams (0.037 mole) of anhydrous aluminum chloride. The slurry thus formed is stirred and heated at 65 C. under an atmosphere of nitrogen for fifteen minutes. During the next six hours, 10 grams (0.075 mole) of anhydrous aluminum chloride in about 2-gram portions are added to the reaction mixture while continuing to heat at 65 C. The mixture is then stirred at 60 C. overnight. Thereafter, excess n-butyl chloride is distilled off as the temperature is gradually increased to about 100 C. The slurry is then stirred at 100 C. for thirty minutes. The mixture is then washed with water and further purified as described in Example I. A benzene-soluble, blackof the test lubricant and its acid number, are determined at the beginning and the conclusion of each test. The percent increase in viscosity and the increase in acid number of the lubricant during the test is indicative of the oxidation stability of the test lubricant at a temperature of 450 F. At'the end of each test an observation is also made as to whether or not varnish and/or sediments are present. The make-up and test results of the lubricants tested are shown in Table I.

TABLE I A B O D E F Composition, percent by Weight:

Pentaerythritol ester lubricant 100 98 98 98 99 98. 9 Phenothiazine 2 t-Butylphenothiazines 2 0. 1 3,7-diocty1ph enothiazine 2 2 N-phenyl-l-naphthylamine 1 1. Oxidation test (air flowzl 1/hr.); viscosity cs. at 100 F.:

Initial 26. 85 27. 30 27. 25 27. 10 27. 37 27. 40 After 20-hour test 53. 70 33. 39 35. 29 40. 03 39. 84 34. 20 Increase. 26. 85 6. 09 8. 04 12. 93 12. 47 6. 80 Percent increase in viscosity 100. 0 22. 31 29. 51 47. 69 45. 58 24. 81 Acid number (ASTM D 974) Initial 0. 06 0. 05 0. 05 0. 06 0. 04 O. 04 After 20-hour te 8. 16 1.21 3. 22 7. 60 6. 88 3. 78 Increasa 8. 10 1. 16 3. 17 7. 54 6. 84 3. 74 Visual observation-Amount of sediment Heavy Trace Trace None Trace amine.

green, soft material (8.9 grams) is obtained. Gas chromatography of the product shows three strong peaks. The low voltage mass spectrum shows that these peaks correspond to phenothiazine (m/e 199), n-butylphenothiazine (m/e 255) and di-n-butylphenothiazine (m/e 311). A trace amount of tri-n-butylphenothiazine is also indicated to be present (m/e 367).

The infrared spectrum (film) of the product has bands at: 3500 cm. (strong N-H), about 3000, 1450-1500, and 1375 cm.- (strong alkyl C-H), about 3100 and 1610 cm.- (aromatic C-H), 1300, 1180, 1160, 1130, 1080, 1040, 1000, 960, 930, 860-880 (s.), 810-830 (s.), 740-750 (s.), 715 and 690 cmr When the product is extracted with n-hexane, the n-hexane-insoluble gray solid (1.5 g.) according to gas chromatography, consists of phenothiazine and some n-butylphenotbiazine. The n-hexane-soluble material is shown by gas chromatography to consist of n-butylphenothiazine and di-n-butylphenothiazine. The infrared spectrum of this material has bands at 3500 cm." (N-H), 3000, 1450- 1500 and 1375 cm.- (alkyl C-H) and 880, 815, 790, 745 cm." (aromatic substitution).

Alkyl-substituted phenothiazines other than nand t-butylphenothiazines are prepared according to the above procedure by replacing the n-buty1 chloride and t-butyl chloride with other alkyl halides including, by way of example, isopropyl chloride, isoamyl chloride, n-hexyl chloride, n-heptyl chloride, n-octyl chloride, t-octyl chloride, n-decyl chloride and n-dodecyl chloride. While the chlorides are preferred, I can also use the corresponding bromides and iodides.

Although it is well-known that alkylphenothiazines are antioxidants for mineral and synthetic oils, the effectiveness of the alkylphenothiazines synthesized by the direct alkylation process of the invention is demonstrated in comparative oxidation tests described hereinafter. In these tests, a synthetic ester-based lubricant, i.e., a pentaerythritol ester lubricant Hercolube J, is used alone and with phenothiazine, with a mixture of t-butylphenothiazines, with 3,7-dioctylphenothiazine, with N-phenyl-l-naphthylamine and with a mixture of t-butyl phenothiazines and N-phenyl-l-naphthylamine. The tests are conducted by bubbling air at a rate of one liter per hour through approximately twenty milliliters of test lubricant contained in a glass test tube inserted into an aluminum block heated to 450 F. The duration of the test is 20 hours. The viscosity The data in the above Table I clearly show that while phenothiazine improves the oxidation stability of the ester-based lubricant, the phenothiazine gives rise to a heavy sediment (Composition B). The t-butylphenothiazines, on the other hand, improve the oxidation stability of the oil without causing the formation of sediment (Composition C). While the commercial antioxidant, 3,7- dioctylphenothiazine produced by thionation of dioctyldiphenylar'nine, improves the oxidation stability of the oil without causing the formation of sediment (Composition D), the 3,7-dioctylphenothiazine is less effective than the t-butylphenothiazines prepared by direct alkylation of phenothiazine with t-butyl chloride. The cooperative effect obtained with a combination of t-butylphenothiazines and a secondary aromatic amine antioxidant, i.e., N-phenyl-1-naphthylamine,is illustrated by comparing Composition F with Compositions C and E. Even though the amount of t-butylphenothiazines in Composition F (0.1%) is considerably less than thatin Composition C (2%), the percent increase in visocstiy in Composition F is less than that in either Composition C or E. It will be noted further by comparing Compositions E and F that the addition of 0.1% of t-butylphenothiazines to Composition E reduces both the percent increase in viscosity and the increase in acid number.

While my invention has been described above with reference to various specific examples and embodiments, it will be understood that the invention is not limited to such examples and embodiments and may be variously practiced within the scope of the claims hereinafter made.

I claim:

1. A process for the preparation of alkyl-substituted phenothiazines having the formula IiI where R is an alkyl radical having from 1 to 12 carbon atoms, a is an integer of 0 to 4 and b is an integer of 1m 4, said process comprising reacting phenothiazine and an excess over the stoichiometric amount of an alkyl halide having from 1 to 12 carbon atoms in the alkyl radical in the presence of an aluminum halide catalyst at a term perature of about 50 to about 200 C. and separating alkyl-substituted phenothiazines from the reaction mass.

2. A process for the preparation of alkyl-substituted phenothiazines having the formula where R is an alkyl radical having from 1 to 12 carbon atoms, a is an integer of to 4 and b is an integer of 1 to 4, said process comprising reacting phenothiazine and an alkyl halide having from 1 to 12 carbon atoms in the alkyl radical in the presence of an aluminum halide catalyst at a temperature of about 50 to about 200 C., the alkyl halide comprising about 2 to about moles per mole of phenothiazine and the aluminum halide comprising about 0.01 to about 1.5 moles per mole of phenothiazine, and separating alkyl-substituted phenothiazines from the reaction mass.

3. The process of claim 2 wherein the alkyl halide is an alkyl chloride and the aluminum halide is anhydrous aluminum chloride.

4. A process for the preparation of t-butylphenothiazines which comprises reacting phenothiazine and t-butyl chloride in the presence of anhydrous aluminum chloride at a temperature of about 50 to about 200 C., the tbutyl chloride comprising about 2 to about 10 moles per mole of phenothiazine and the aluminum chloride comprising about 0.01 to about 1.5 moles per mole of phenothiazine, and separating t-butylphenothiazines from the reaction mass.

5. The process of claim 4 wherein the mole ratio of phenothiazine to t-butyl chloride to anhydrous aluminum chloride is 1:5 1.1, respectively.

6. A process for the preparation of n-butylphenothiazines which comprises reacting phenothiazine and nbutyl chloride in the presence of anhydrous aluminum chloride at a temperature of about to about 200 C., the n-butyl chloride comprising about 2 to about 10 moles per mole of phenothiazine and the aluminum chloride comprising about 0.01 to about 1.5 moles per mole of phenothiazine, and separating n-butylphenothiazines from the reaction mass.

7. The process of claim 6 wherein the mole ratio of phenothiazine to n-butyl chloride to anhydrous aluminum chloride is 1 :9 1.1, respectively.

References Cited R. Olah: Friedel-Crafts and Related Reactions, vol. H, p. 417-21 (1964) (Interscience Publ.).

S. Baltzly et al.: J. Am. Chem. Soc., vol. 68, pp. 2673- 78 (1946).

HENRY R. JILES, Primary Examiner H. I. MOATZ, Assistant Examiner US. Cl. X.R. 25247 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3'589'484 Dated p ember 5, 1972 lnventofls) Ilgvars J. Spilners It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 31, "octylpheothiazine" should read octylphenothiazine line 52, "phenolthiazine" should read phenothiazine line 71, "ad" should read and Column 2, line 2, "2,484,838" should read 2,483,838

Column 5, line 59, "btuyl" should read butyl Column 6, line 67, "0.01" should read 0.1

Signed and sealed this 23rd day of January 1973.,

(SEAL) Attests EDWARD M.FLETCHER,JR. 7 ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

